The CTS system administration team has been working through the night on this problem.
The copying of users’ email folders continued through the night, but early estimates of the progress were overly optimistic. As of 6:00 am today (Friday), about 2/3 of the data has been moved from the drive that failed, onto a new drive. Half a terabyte remains to be copied.
Experiments with restoring access to the copied folders, while also keeping mail that has been delivered during the last day, show that this is trickier than originally thought. Work is ongoing.
We apologize for inconvenience. Rest assured our system administration team has restoring email service as their top priority.